Composite yarn, preparation method thereof and elastic fabric

ABSTRACT

The present invention relates to a composite yarn, a preparation method thereof and an elastic fabric, wherein the composite yarn comprises a core yarn and an outer wrapping yarn, wherein the core yarn further comprising at least one piece of elastic filament, and wherein the outer wrapping yarn is made of short fiber, wherein the outer wrapping yarn is spirally wrapped on the core yarn, wherein drafting ratio of the core yarn is 1-1.5 times.

TECHNICAL FIELD

This disclosure generally relates to the technical field of textiles,and more particularly, to a composite yarn, a method of preparationthereof and an elastic fabric.

BACKGROUND

As a fashion clothing, jeans has always been popular among consumers(especially teenagers) for more than a century. The denim fabric isformed by interweaving a classic indigo-blue pure cotton yarn and awhite pure cotton yarn into a crow-twill structure. However, as timepasses, people start to demand more on the comfort of the clothing otherthan just design and style. To meet the demand, an elastic fabric isdeveloped to replace the conventional non-elastic denim fabric, whichallows people to move more freely and comfortably.

Reducing the weft shrinkage of the high-elastic denim fabric normallyemploys the following methods: first, performing a high-temperatureshaping in the post-finish process; second, performing pre-shrinkingmultiple times; third, heating and washing the prepared denim fabricusing a dye vat. However, the aforesaid methods reduce the shrinkagerate by means of a post-finish processing instead of solving theshrinkage problem at the beginning of the process, resulting in long andcomplex production process, high production cost and poor productquality.

The elastic fabric is generally formed by interweaving a weft yarn and awarp yarn, wherein the weft yarn is made of an elastic yarn (i.e., acore yarn), which endows the fabric with a certain elasticity. A coreyarn takes an elastic filament as a core, and the exterior of theelastic filament is wrapped by a non-elastic short fiber. As short fibershrinks after being heated due to high water-absorption rate, theconventional core yarn structure makes the shrinkage rate of the elasticfabric unstable. The conventional core yarns are mainly divided into asingle core yarn and a double core yarn. During the spinning process,the elastic filament is wrapped by a rough yarn made of a short fiber ona spinning machine, and after drafting, twisting and winding, acomposite yarn is obtained. Typically, the core yarn adopts a low denierfilament having a large drafting ratio (the drafting ratio is 2-4 timesand normally 3.5 times or more). If the degree of twisting isexcessively low when the elastic filament is wrapped by the short fiberrough yarn, the fiber cannot be tightly held by the rough yarn, and as aresult, the inner and outer fiber become loose easily. Consequently, theshrinkage rate of the fabric made from the aforesaid yarn is high.Meanwhile, during the wrapping, weaving and post-finishing (especiallyduring the high temperature shaping), the elastic filament can beseverely damaged. Under such circumstances, when the finished garment iswashed with water (using physical and chemical methods), the elasticfilament can be further damaged such that local loss of elasticity mayoccur. Contrarily, if the degree of twisting is excessively high whenthe elastic filament is wrapped by the short fiber rough yarn, althoughthe shrinkage of the prepared fabric is relatively small, the elasticityof the fabric will be low and the corresponding tensile force will behigh, making the garment uncomfortable to wear.

Moreover, if the shrinkage rate of the elastic fabric cannot be stablycontrolled, serious curling occurs when the fabric is cut, and the sizeof the garment becomes unstable after sewing, leading to the poorquality of products. Therefore, as previously mentioned, the elasticfabric needs to undergo a post-finish process to address this issue.When the fabric goes through the post-finishing, the fabric typicallyshrinks by 5%-7%, and the width of the fabric is reduced accordingly.After the post-finish process is completed, especially after thepre-shrinking and high-temperature shaping are ended, the shrinkage rateof the prepared fabric can be generally controlled at −10%˜−16%,however, its width will only be 60-70% of the original fabric.

Presently, there is a covering yarn sold on the market, which is alsoknown as a wrapping yarn. It is a yarn having a novel structure, whichuses a chemical fiber filament yarn as the core yarn, and uses anotherchemical fiber filament yarn as the outer wrapping yarn, wherein theouter wrapping yarn wraps around the core yarn in a spiral manner.Because the water absorption rate of the chemical fiber filament yarn islow, the shrinkage rate of the fabric prepared by using the wrappingyarn is also low. The wrapping yarn having the aforesaid structure isprimarily used for preparing the knitted fabric. Because the tactilityof the woven fabric is poor and the elasticity is low, it is notsuitable for the preparation of denim fabric.

In conclusion, how to make the elastic fabric maintain a certainelasticity (preventing the loss of elasticity from occurring), how toguarantee a stable and low shrinkage rate and maintaining the size ofthe fabric, and how to achieve an ideal retro effect of the fabric aretechnical problems that hinder the development of elastic fabric andneed to be solved urgently.

SUMMARY

The present invention discloses a composite yarn, a preparation methodthereof and an elastic fabric. According to the present invention, thetechnical problems relating to the high shrinkage rate and low stabilityof elastic fabric caused by core yarn wrapped with outer wrapping yarnmade of short fiber are effectively solved.

The present disclosure adopts the following technical solution: acomposite yarn comprising a core yarn and an outer wrapping yarn,wherein the core yarn is composed of at least one elastic filament, andthe outer wrapping yarn is made of short fiber, wherein the outerwrapping yarn is spirally wrapped around the core yarn, and the draftingratio of the corn yarn is 1-1.5.

In another embodiment of the present invention, the degree of twistingof the outer wrapping yarn is 8.48-36 twists/inch, and the length of theouter wrapping yarn is more than 1.5 times that of the core yarn.

In another aspect of the present invention, the number of winding turnsof the outer wrapping yarn on the core yarn is more than 15 per 1 cm(centimeter).

In another aspect of the present invention, the number of winding turnsof the outer wrapping yarn on the core yarn is 15-40 per 1 cm(centimeter).

In another aspect of the present invention, the counts of the outerwrapping yarn are 10-80S, and the denier of the core yarn is 20D-500D.

In another aspect of the present invention, the short fiber is a fiberhaving a length ranging from 10-90 mm (millimeter), and the short fiberis a natural fiber or a chemical fiber.

In another aspect of the present invention, the short fiber is a cottonfiber, a tencel fiber, a modal fiber, a polyester fiber or a nylonfiber.

In another aspect of the present invention, the short fiber is a cottonfiber.

A preparation method of the composite yarn, comprising the steps of:

Processing the short fiber into a rough yarn, and processing the roughyarn into an outer wrapping yarn through a spinning process;

Placing a corn-yarn spool on a feeding roller, drawing the core yarninto a hollow spindle through a pre-drafting roller, and imposing adrafting force having a drafting ratio of 1-1.5 times on the core yarnby the pre-drafting roller;

Feeding the core yarn into the hollow spindle, making the core yarn passthrough the center of the hollow spindle, and leading out the outerwrapping yarn along with the rotation of the hollow spindle, thus makingthe outer wrapping yarn wrap on the hollow spindle; finally, through anair-ring guiding hook, a yarn-guiding roller and a pressing roller,winding to obtain a finished composite yarn, wherein during the wrappingprocess, the twisting degree of the outer wrapping yarn is 900-1500twists/m.

An elastic fabric, formed by interweaving a warp yarn or a weft yarn,wherein the weft yarn comprises the composite yarn.

Compared with the prior art, the present disclosure has the followingadvantages: the composite yarn has an improved structure compared withthe conventional yarn, wherein the elastic filament is wrapped by theyarn made of a short fiber, thus obtaining a novel wrapping yarn; thecomposite yarn of the present invention is used on woven fabric; thewoven fabric shows an ideal retro effect, and has low shrinkage rate andexcellent elasticity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is conceptual diagram illustrating an example structure of thecomposite yarn of the present invention (in a stretched state).

FIG. 2 is conceptual diagram illustrating an example structure of thecomposite yarn of the present invention (in a non-stretched state).

FIG. 3 is a conceptual diagram illustrating a production flow of thecomposite yarn of the present invention.

FIG. 4 is a conceptual diagram illustrating a denim fabric having aretro effect of the present invention.

FIG. 5 is a conceptual diagram illustrating a denim fabric having noretro effect of the present invention.

DETAILED DESCRIPTION

The present invention discloses a composite yarn, a preparation methodthereof and an elastic fabric. To better illustrate the purposes,technical solutions and effects of the present invention, the presentinvention is further described in detail below. It should be understoodthat the specific embodiments described herein are merely used toelaborate the present invention and are not used to limit the presentinvention.

In the description of the present invention, it should be understoodthat the orientations or positions indicated by the terms “central”,“longitudinal”, “transverse”, “length”, “width”, “thickness”, “up”,“down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”,“top”, “bottom”, “inside”, “outside”, “clockwise” and “counterclockwise”are based on the orientations or positions shown in the figures, or theorientations or positions that the product of the present invention iscommonly placed during use, or the orientations or positions that arecommonly understood by those skilled in the art. They are merely for theconvenience of describing and simplifying the description of the presentinvention, but not indicating or implying that the equipment or elementreferred to must have a specific orientation, or be constructed andoperated in a specific orientation. Thus, they cannot be understood as alimitation of the present invention. In addition, the terms “first” and“second” are used for descriptive purposes only and cannot be understoodas the indication or implication of relative importance or theimplication of the number of indicated technical features. Thus, atechnical feature defined as “first” or “second” may explicitly orimplicitly comprises one or more technical features. In the descriptionof the present invention, unless being clearly stated, “a plurality of”means two or more.

In the description of the present invention, unless being clearlystated, the terms “installation” and “connection” shall be understood ina broad sense. For instance, it may be a fixed connection, a detachableconnection, a mechanical connection, an electrical connection, a directconnection, an indirect connection through an intermediate medium, aninternal connection of two components or an interaction between twocomponents. For those skilled in the art, the specific meanings of theabove terms in the present invention may be understood according tospecific circumstances.

In the description of the present invention, unless being clearly statedand specified, the first feature being “above” or “below” the secondfeature may indicate a direct contact between the first and secondfeatures or an indirect contact between the first and second featuresthrough other features. Moreover, the first feature being “above” thesecond feature may indicate that the first feature is directly above orobliquely above the second feature, or merely indicates that thehorizontal height of the first feature is higher than that of the secondfeature. The first feature being “below” the second feature may indicatethat the first feature is directly below or obliquely below the secondfeature, or merely indicates that the horizontal height of the firstfeature is lower than that of the second feature.

The following description discloses various embodiments for implementingvarious structures of the present invention. To simplify the descriptionof the present invention, components and arrangements of specificembodiments are described below. Definitely, they are merely examplesand are not intended to limit the present invention. Furthermore, in thepresent invention, reference numerals and/or reference letters indifferent embodiments may be repeated for the purpose of simplificationand clarity, which does not indicate the relationship between variousembodiments and/or arrangements discussed. Additionally, the presentinvention discloses embodiments of various processes and materials,which allow those skilled in the art to associate themselves with theapplication of other processes and/or the use of other materials.

The present invention discloses a composite yarn, with an improvedstructure compared with the conventional outer wrapping yarn. As shownin FIGS. 1-2, the composite yarn of the present invention comprises acore yarn 21 and an outer wrapping yarn 6. The core yarn 21 is composedof at least one piece of elastic filament, and the outer wrapping yarn 6is a yarn made of a short fiber. The outer wrapping yarn 6 is spirallywrapped on the core yarn 21. When the composite yarn is not in astretched state, the outer wrapping yarn 6 is spirally wrapped on thecore yarn 21 with even spacing, such configuration is capable ofpreventing exposing of the elastic filament and protecting againstdamage. The twisting degree of the outer wrapping yarn 6 is 8.48-36twists/inch, and the drafting ratio of the core yarn 21 is 1-1.5 times.The length of the outer wrapping yarn 6 is more than 1.5 times that ofthe core yarn 21, and the number of winding turns of the outer wrappingyarn 6 on the core yarn 21 is more than 15 per 1 cm (centimeter).

In the technical solution of the present invention, the length of thecomposite yarn refers to a section of the finished composite yarn cutout for measurement. The length of the outer wrapping yarn 6 refers tothe length after being tensioned, which is more than 1.5 times of thelength of the core yarn 21. The length of the core yarn 21 refers to thelength of the portion located within the composite yarn in a tensionedstate, which is equal to the length of the composite yarn.

The outer wrapping yarn 6 is a single yarn, and its original twistingdegree is 8-30 twists/inch before the wrapping process. After beingtwisted and wrapped, the twisting degree of the outer wrapping yarn 6increases by 6-20%, and its twisting degree reaches 8.48-36 twists/inch.

The drafting ratio refers to tensioning the elastic filament using acertain tension force. For instance, if the drafting ratio is 2 times,the length increases by 2 times.

According to the technical solution of the present invention, thedrafting ratio of the core yarn 21 is 1-1.5. The small drafting ratio ofthe core yarn 21 has the following advantages:

Because the drafting ratio of the core yarn 21 in the composite yarn issmall, the tensile property of the core yarn 21 protects the core yarn21 from being excessively tensioned even if it is pulled during theweaving process thus significantly reduce damage to the core yarn 21.

In the high temperature treatment, the damage to the elastic filament ina tensioned state is greater than that to the elastic filament in anatural state. Therefore, in the post-finishing process, the hightemperature of the shaping treatment causes less damage to the elasticfilament with smaller drafting ratio. Thus, an excellent elasticperformance is ensured.

When the finished garment is washed, especially at the sewing positions,as the core yarn 21 is in a low tensile state, and the resilience of thecore yarn 21 is low. Therefore, the shrinkage of the core yarn 21 andthe outer wrapping yarn 6 is relatively synchronous, which effectivelyprevents loss of elasticity as well as bulges at seam joints and frontzipper.

The small drafting ratio and the low resilience of the elastic filamentmake the elastic filament stretch more easily and recover to its naturalstate to improve the comfortness of the fabric.

The elastic filament of the core yarn 21 does not need to be tensionedfor a long time, reducing the probability of elastic fatigue. Theelastic filament maintains high tensile and resilient properties, andthe core yarn 21 can maintain stable elasticity for a long period oftime, meaning that the elasticity of the composite yarn is stable.

During the wrapping process, the outer wrapping yarn 6 is also twisted,allowing the fiber in the outer wrapping yarn 6 to be held morecompactly. As the friction between the fiber increases, the inner andouter migrations of fiber become difficult such that the fabric made ofthis composite yarn has high stability. Preferably, the twisting degreeof the outer wrapping yarn 6 is controlled to be 900-1500 twists/m(meter). When the twisting degree of the outer wrapping yarn 6 isproperly controlled, it can be evenly spirally wrapped on the core yarn21, achieving good wrapping and shaping effects. Meanwhile, it is noteasy for the fiber to slide, which effectively reduces the shrinkage ofthe fabric. Moreover, properly increasing the twisting degree preventsthe composite yarn structure from distorting due to theexcessively-tight holding. If the composite yarn distorts, the tactilityof the fabric may be affected causing skin itchiness. Due to the smalldrafting ratio of the elastic filament, the low resilience allows theelastic filament to stretch naturally significantly reduces damages tothe elastic filament. Additionally, the wrapping process makes the innerand outer migrations of the fibers in the yarn more difficult. frictionbetween fibers increases, which in turn increases the hardness of theyarn. When the composite yarn is used for weaving as a warp yarn or aweft yarn, the friction in the weaving area is greater, which makes theyarn difficult to slide. Therefore, after the regular post-finishingprocess, the shrinkage rate of the fabric made of the composite yarn isstable and small. After each process, the shrinkage rate variesslightly, and the fabric width varies slightly, which makes the width ofthe finished fabric reach 80-90% of that of the original fabric. As thesurface of the core yarn 21 is spirally wrapped by the outer wrappingyarn 6, when the fabric is tensioned, the length of the outer wrappingyarn 6 enables the fabric to be effectively stretched, and when thefabric is tensioned to a certain degree, the performance of the outerwrapping yarn 6 prevents the fabric from continuously being stretched,thus protecting the core yarn 21 against the damage caused by anexcessive stretching of the fabric. Meanwhile, the spiral wrappingmethod is to make the outer wrapping yarn 6 rotate, twist and thenspirally wrap the core yarn 21 in the form of circles. The squeezingforce imposed by the outer wrapping yarn 6 on the core yarn 21 isrelatively small, allowing the elastic filament to stretch and contractfreely. Moreover, the drafting ratio of the elastic filament is small,ensuring that the composite yarn has excellent elasticity. Thus, thefabric woven with the composite yarn also has excellent elasticity.However, in the preparation process of the conventional composite yarn,the elastic filament is wrapped by rough yarn made by short fiber whilebeing twisted. The elastic filament is greatly restricted due to thegreater twisting degree which result in greater pressure borne by theelastic filament.

In the present invention, the length of the outer wrapping yarn 6 is atleast 1.5 times that of the core yarn 21, and the number of windingturns of the outer wrapping yarn 6 on the core yarn 21 is more than 15per 1 cm (centimeter). In this way, the surface of the core yarn 21 isevenly wrapped by the outer wrapping yarn 6, which prevents the coreyarn 21 from exposing such that the core yarn 21 is effectivelyprotected against the damage caused by friction. Preferably, the numberof winding turns of the outer wrapping yarn 6 on the core yarn 21 is15-40 per 1 cm (centimeter). In this range, the yarn can be evenlywrapped on the elastic filament, and the loops can be closely connectedwithout squeezing each other.

In the present invention, the counts of the outer wrapping yarn 6 can be10-80S, and the denier of the core yarn 21 can be 20D-500D. The countsof the outer wrapping yarn 6 should not be excessively high, because thehigher the counts of yarn are, the lower the strength of the yarnbecomes. Moreover, it makes the yarn easy to break during wrapping,creating quality problems. As for the unit of yarn count, S representsthe counts of yarn in an English system, which refers to how many840-yards contained in the total length of one pound of yarn at theconventional moisture regain. D is the abbreviation of Denier, whichrepresents the fineness of chemical fiber. It refers to the weight(grams) of 9000-meter-long filament at the conventional moisture regain.

In the present invention, the outer wrapping yarn 6 must be a yarn madeof a short fiber having a length ranging from 10-90 mm (millimeter). Theshort fiber can be a natural fiber or a chemical fiber, including cottonfiber, tencel fiber, modal fiber, polyester fiber or nylon fiber, etc.Preferably, the short fiber is a cotton fiber, because cotton fiber isnatural, common, skin-friendly and has good tactility.

The core yarn 21 is made of an elastic filament, including apolyurethane filament, a polyolefin filament, a rubber filament or atwo-component filament, etc.

The conventional structure of the wrapping yarn is to wrap the elasticfilament using a chemical filament. However, the tactility of the wovenfabric is poor, its elastic elongation is low, it is difficult tostretch and the retro effect is poor. In the technical solution of thepresent invention, the structure of the conventional wrapping yarn isimproved, wherein the elastic filament is wrapped by the yarn made of ashort fiber. After being used for weaving, the woven fabric shows anideal retro effect, and has low shrinkage rate and excellent elasticity.

Conventional core yarns are primarily single core yarn and a double coreyarn. During the spinning process, elastic filament is wrapped by arough yarn made of a short fiber on a spinning machine, and afterdrafting, twisting and winding, a composite yarn is obtained. Typically,the core yarn is a low denier filament having a large drafting ratio. Ifthe twisting degree is excessively low when the elastic filament iswrapped by the short fiber rough yarn, the fiber cannot be tightly held,and inner and outer fiber migrations may easily occur. As a result, theshrinkage rate of the fabric made from the aforesaid yarn is high.Meanwhile, during the wrapping, weaving and post-finishing (especiallyduring the high temperature shaping), the elastic filament may beseriously damaged. Under such circumstances, when the finished garmentis washed with water (using physical and chemical methods), the elasticfilament may be further damaged such that a local loss of elasticity mayoccur. Contrarily, if the twisting degree is excessively high when theelastic filament is wrapped by the short fiber rough yarn, although theshrinkage of the prepared fabric is relatively small, the elasticity ofthe fabric is low and the tensile force required is large, making thegarment uncomfortable to wear.

The composite yarn is prepared by using the outer wrapping yarn 6 towrap the elastic filament. The outer wrapping yarn 6 in the compositeyarn spirally wraps the elastic filament in the form of circles. Thesqueezing force imposed by the outer wrapping yarn 6 on the elasticfilament is smaller than that imposed by the conventional one, and thefiber in the composite yarn are held more tightly. As the inner-layerelastic filament has a small drafting ratio, it may be freely stretchedsuch that the elastic filament is less controlled by the outer wrappingyarn 6. Thus, during the weaving or post-finishing process, especiallyduring the high temperature shaping, the damage to the inner-layerelastic filament is small, achieving an excellent elastic performance ofthe fabric. Moreover, the twisting degree of the outer wrapping yarn ishigher than that of the conventional rough yarn, which enables the fiberin the yarn to be held more closely while making the inner and outermigrations of the fiber more difficult. Therefore, a high stability ofthe fabric size is achieved.

The present invention discloses a preparation method of the compositeyarn, which primarily utilizes a hollow spindle for wrapping. The hollowspindle spinning utilizes the rotation of the hollow spindle to propelthe outer wrapping yarn 6 to rotate, thus enabling the outer wrappingyarn 6 to spirally wrap the core yarn 21 through the hollow spindle.During wrapping, the core yarn 21 passes through the hollow position ofthe hollow spindle from the feeding roller, and the drafting ratio ofthe core yarn 21 is 1-1.5 times. Subsequently, the outer wrapping yarn 6is spirally wrapped on the core yarn 21. By changing the twistingdegree, the yarn can be evenly wrapped on the elastic filament.

Specifically, the preparation method of the composite yarn, comprisingthe steps of: Processing the short fiber into a rough yarn, andprocessing the rough yarn into an outer wrapping yarn 6 through aspinning process;

Placing a corn-yarn spool on a feeding roller, drawing the core yarn 21into a hollow spindle through a pre-drafting roller, and imposing adrafting force having a drafting ratio of 1-1.5 times on the core yarn21 by the pre-drafting roller;

Feeding the core yarn 21 into the hollow spindle, making the core yarn21 pass through the center of the hollow spindle, and leading out theouter wrapping yarn 6 along with the rotation of the hollow spindle,thus making the outer wrapping yarn 6 wrap on the hollow spindle;finally, through an air-ring guiding hook, a yarn-guiding roller and apressing roller, winding to obtain a finished yarn.

Furthermore, the preparation method of the composite yarn, comprisingthe steps of:

Placing a corn-yarn spool 2 on a feeding roller, and releasing the cornyarn 21 through propelling the corn-yarn spool 2 to rotate; making thecore yarn 21 pass through a hollow spindle 5 of the spinning machinethrough a tangential belt 4 at a certain drafting ratio under the actionof a pre-drafting roller, thus making the corn yarn to move linearly;subsequently, placing the outer wrapping yarn 6 on the hollow spindle 5,and making the hollow spindle 5 run at a high speed under the action ofa transmission mechanism, thus unwinding the outer wrapping yarn 6 at acertain speed and allowing the outer wrapping yarn to evenly wrap thecorn yarn 21 moving linearly to form a composite yarn; making thecomposite yarn pass through an air-ring guiding hook 8 to control thefixed position of the composite yarn; finally, through a guiding roller9, a pressing roller 10, a reciprocating guide device 11 and a curlingroller 12, winding the composite yarn on a spool 13 parallel to theouter wrapping yarn.

In the wrapping process, the twisting degree of the outer wrapping yarn6 is 900-1500 twists/m.

The present invention is further described through the followingembodiments:

Embodiment 1

The warp yarn is a 10S pure cotton yarn, and the weft yarn A1 is a 15Spure cotton+180D spandex single core yarn, wherein the drafting ratio ofthe spandex is 3.5 times, and the warp yarn is interwoven with the weftyarn A1 to form a fabric 1. The weft yarn A2 adopts a 15S pure cottonyarn spirally wrapping a 180D spandex, wherein the drafting ratio of thespandex is 1.5 times, and the warp yarn is interwoven with the weft yarnA2 to form a fabric 2. Fabric 1 and fabric 2 are 3/1 twill structures.

Fabric 1 and fabric 2 are processed by the following conventionalpost-finishing process:

In a singeing machine, the temperature of the flame is controlled to be800° C., and the speed of the singeing vehicle is controlled to be 70m/min, wherein the singeing process adopts a two-face-one-back singeing,namely, the front side of the fabric is singed twice, and the back sideof the fabric is singed once;

A desizing machine is used to perform a desizing process; when desizing,the concentration of the desizing enzyme is 12 g/L and the concentrationof the penetrant is 8 g/L; the temperature of the size vat is set at 70°C., the temperature of the washing tank is set at 65° C., thetemperature of the drying drum is set at 110° C., the rolling pressureis set at 0.35 Mpa, the desizing speed is controlled at 65 m/min fordesizing, and the falling-cloth humidity is controlled at 4%;

A pre-shrinking machine is used to perform a pre-shrinking process,wherein the speed is 30 m/min, the compression degree of the rubberblanket is 18%, the temperature of the rubber blanket is 140° C., andthe temperature of blanket drying drum is 140° C.

After the performances of fabric 1 and fabric 2 are tested, the testresults are shown in table 1.

The standard of the elasticity test consists of testing the tensileelastic properties of woven fabrics, such as elastic elongation, elasticresilience and growth rate (namely, plastic deformation) according tothe standard FZ/T 01034-2008 “Test Method for Tensile Elasticity ofWoven Fabrics”.

The standard of the shrinkage test is based on the standard AATCC135-2015 “Variation of Fabric Size in Home Launder”.

The width test is performed by measuring the cloth size with a ruler.

TABLE 1 Width of finished Width Width Width product after of grey afterafter pre- Weft Elastic Growth Elastic fabric singeing desizingshrinking shrinkage elongation rate resilience (inch) (inch) (inch)(inch) (%) (%) (%) (%) Fabric 1 66 63 53.2 49.5 −13 66 6.5 88.9 Fabric 264 63 57.6 55 −3 70.5 2.3 95.6

Among them, the width of the finished fabric 1 accounts for 75% of thewidth of the grey fabric, and the width of the finished fabric 2accounts for 85.94% of the width of the grey fabric.

Through comparison, it can be seen that the shrinkage rate of the fabricwoven with the composite yarn of the present invention is wellcontrolled, the width of the finished fabric is large, and theproduction efficiency is significantly improved.

The weft shrinkage refers to the shrinkage rate of the finished fabric.The shrinkage rate of the finished fabric 1 is −13% while that of thefinished fabric 2 is −3%, which proves that the size stability of fabric2 is much higher. Meanwhile, the elastic elongation and the elasticresilience of fabric 2 are high, and the growth rate is small.Therefore, after a prolonged period of stretching, the resilience offabric 2 is good, and the probability of plastic deformation is low.

Through unaided eye observation, fabric 1 has no retro effect, its twillsense is weak and its wrinkle effect is poor, while fabric 2 has anideal retro style, its twill sense is strong and its texture is clear.

Embodiment 2

The warp yarn is interwoven with cotton and tencel, the counts of yarnis 16S, and the weft yarn B1 is a 21S+105D core yarn, wherein thedrafting ratio of the spandex is 3.5 times, and the warp yarn isinterwoven with the weft yarn B1 to form a fabric 3. The weft yarn B2adopts a 21S pure cotton yarn spirally wrapping a 105D spandex, whereinthe drafting ratio of the spandex is 1.5 times, and the warp yarn isinterwoven with the weft yarn B2 to form a fabric 4. Fabric 3 and fabric4 are 3/1 twill structures.

Fabric 3 and the fabric 4 are processed by the same conventionalpost-finishing process in embodiment 1.

After the performances of fabric 3 and fabric 4 are tested, the testresults are shown in table 2.

TABLE 2 Width of Width Width Width finished of grey after after productafter Weft Elastic Growth Elastic fabric singeing desizing pre-shrinkingshrinkage elongation rate resilience (inch) (inch) (inch) (inch) (%) (%)(%) (%) Fabric 3 70 64 55 48 −15 72 7.6 90.3 Fabric 4 66 62 58 56 −3 752.9 94.8

Among them, the width of the finished fabric 3 accounts for 68.57% ofthe width of the grey fabric, and the width of the finished fabric 4accounts for 84.85% of the width of the grey fabric.

Through comparison, it can be seen that the shrinkage rate of the fabricwoven in the composite yarn of the present invention is well controlled.The width of the finished fabric is relative large, and the productionefficiency is significantly improved.

The weft shrinkage refers to the shrinkage rate of the finished fabric.The shrinkage rate of the finished fabric 3 is −15% while that of thefinished fabric 4 is −3%, which proves that the size stability of fabric4 is much higher. Meanwhile, the elastic elongation and the elasticresilience of fabric 4 are large, and the growth rate is small.Therefore, after a prolonged period of stretching, the resilience offabric 2 is good, and the probability of plastic deformation is low.

Through unaided eye observation, fabric 3 has no retro effect, its twillsense is weak and its wrinkle effect is poor, while fabric 4 has anideal retro style, its twill sense is strong and its texture is clear.

It should be understood that the scope of the present invention is notlimited to the embodiments described above. For those skilled in theart, various improvements and modifications may be made withoutdeparting from the principles of the present invention. Therefore, theseimprovements and modifications shall also fall into the scope of thepresent disclosure.

What is claimed is:
 1. A composite yarn, comprising: a core yarn, and anouter wrapping yarn, wherein the core yarn further comprising at leastone piece of elastic filament, and wherein the outer wrapping yarn ismade of short fiber, wherein the outer wrapping yarn is spirally wrappedaround the core yarn, and the drafting ratio of the corn yarn is 1-1.5times.
 2. The composite yarn of claim 1, wherein the twisting degree ofthe outer wrapping yarn is 8.48-36 twists/inch, and wherein length ofthe outer wrapping yarn is more than 1.5 times that of the core yarn. 3.The composite yarn of claim 1, wherein number of winding turns of theouter wrapping yarn on the core yarn is greater than 15 per 1 cm.
 4. Thecomposite yarn of claim 1, wherein number of winding turns of the outerwrapping yarn on the core yarn is 15-40 per 1 cm.
 5. The composite yarnof claim 1, wherein counts of the outer wrapping yarn are 10-80S, anddenier of the core yarn is 20D-500D.
 6. The composite yarn of claim 1,wherein the short fiber is a fiber having a length ranging from 10-90mm, and wherein the short fiber is a natural fiber or a chemical fiber.7. The composite yarn of claim 1, wherein the short fiber is a cottonfiber, a tencel fiber, a modal fiber, a polyester fiber or a nylonfiber.
 8. The composite yarn of claim 1, wherein the short fiber is acotton fiber.
 9. A preparation method of the composite yarn of claim 1,comprising the steps of: Processing short fiber into a rough yarn, andprocessing rough yarn into an outer wrapping yarn through a spinningprocess; Placing a corn-yarn spool on a feeding roller, drawing the coreyarn into a hollow spindle through a pre-drafting roller, and imposing adrafting force having a drafting ratio of 1-1.5 times on the core yarnby the pre-drafting roller; Feeding the core yarn into the hollowspindle, making the core yarn pass through the center of the hollowspindle, and leading out the outer wrapping yarn along with the rotationof the hollow spindle, thus making the outer wrapping yarn wrap on thehollow spindle; through an air-ring guiding hook, a yarn-guiding rollerand a pressing roller, winding to obtain a finished composite yarn,wherein during the wrapping process, the twisting degree of the outerwrapping yarn is 900-1500 twists/m.
 10. An elastic fabric, comprisinginterweaving a warp yarn or a weft yarn, wherein the weft yarn is thecomposite yarn as described in claim 1.